This invention is directed to methods and apparatus for wrapping straps around articles.
The present invention was developed for use in strapping a bundle of elongate items, e.g., wires, together and is described with reference to such an environment. However, it will be appreciated that the invention can be utilized in other environments to strap other types of items together. In this regard, while wires, when strapped together, form a generally cylindrical bundle, noncylindrical bundles can be strapped using the invention. Moreover, the individual items can be noncircular or even dissimilar. Also, the invention can be used to wrap a strap around a single item, such as a box or a tube. In general any suitably sized article can be wrapped with a strap by the invention. Further, while, as will be better understood from the following description, the preferred strapping material is thermoplastic in nature, other materials that can be bonded using heat and pressure can be utilized. For example, rather than a thermoplastic material, which forms a bond under pressure and ultrasonic vibration as a result of the material softening and flowing together, the strapping material could be coated with an adhesive that is activated to form a bond when force and ultrasonic vibration is applied.
In the past, a wide variety of apparatus has been proposed for wrapping a strap around an article, such as a bundle of wires, together. In some apparatus, individual ties are delivered to a strapping mechanism that wraps the ties around the wires. One end of each tie may include a latch element and the other end a plurality of ratchet elements that coact with the latch element. Other ties use button like elements or rivets to affix the ends of the ties together. These systems have a number of disadvantages. First, individual ties are more expensive than desirable. Secondly, a bulge or protrusion is present in the region of the latch or button. The protrusion sometimes makes it difficult to pull a bundle of strapped wires through relatively small openings, because the protrusion gets caught on the edges of the openings. In addition, the protrusions have been found to abraid adjacent wire bundles when used in regions of high vibration. Also such ties are often formed of materials that deteriorate in high temperature environments.
Because of the disadvantages of latch type ties, many wire bundles are individually hand-tied. While hand-tying overcomes some of the foregoing disadvantages, it is time-consuming and, therefore, expensive. Moreover, hand-tying still results in a protrusion being formed, albeit a protrusion that is usually smaller than the protrusion that is formed by latch type ties.
Therefore, it is an object of this invention to provide a new and improved method and apparatus for strapping an article.
It is another object of this invention to provide a new and improved method and apparatus for forming a protrusionless strap around a bundle of elongate objects.
It is a further object of this invention to provide a new and improved tool for wrapping a strap around a bundle of wires that is, mechanically, relatively uncomplicated.
Another disadvantage of prior art mechanisms for automatically wrapping a strap around a bundle of elongate objects is their utilization of pneumatic and hydraulic power. While pneumatic and hydraulic systems are relatively reliable, they require a source of pneumatic or hydraulic power, which is not always readily available. Contrariwise, electrical power is more readily available in most environments.
Therefore, it is a subsidiary object of this invention to provide an electromechanical apparatus for wrapping a protrusionless strap around a bundle of objects.